Experiments and 3D transient MP-PIC simulations of a circulating fluidized bed reactor

Steelmaking processes that employ circulating fluidized bed reactors (CFBRs) for hydrogen-based iron ore reduction represent a promising, efficient, and environmentally friendly alternative to traditional blast furnace and direct reduction shaft furnace methods. The aim of this study is to develop a simulation model using the multiphase particle-in-cell (MP-PIC) approach, validated against experimental measurements from a lab-scale CFBR. The focus is on particle–fluid interactions in a cold flow model; chemical reactions are not considered. The simulations were performed using the MP-PIC approach, applying various drag correlations, including homogeneous and structure-dependent models, as well as a model that accounts for polydispersity. Experimental results indicate that higher gas flow rates enhance particle entrainment, leading to larger average particle sizes, broader size distributions, greater pressure, and higher solids circulation rates. All these trends are captured by the simulation model. However, comparative analyses reveal distinct differences in predictive capabilities among drag models. The applied homogeneous models overestimate entrainment and pressure, with circulation rates overestimated by factors of 3–4. Conversely, the applied structure-dependent models underestimate these parameters, with circulation rates underestimated by factors of 3–8. The polydisperse model offers slight advantages in capturing the system’s polydispersity. The study underscores the need to refine drag models to account for system-specific conditions, enhancing predictive accuracy across diverse flow conditions. The findings advance the understanding of CFBR hydrodynamics and provide the basis for potential optimization strategies for upscaling.